\begin{tikzpicture}
	\begin{scope}
		\tkzDefPoints{0/0/A, 2/0/B, 3/0/C,  -3/0/a, -1/0/b}
		\tkzDrawSegment[xianduan={below=0pt}](a,b)
		\tkzLabelSegment[above](a,b){$a$}
		\tkzDrawLine[add=0 and 0.1](A,C)
		\tkzLabelLine[pos=1.1,right=1em](A,C){甲}
		\tkzDrawSegment[xianduan={below=0pt}](A,B)
		\tkzDrawSegment[dim={$20$,-10pt,}](A,B)
		\tkzLabelPoints[above=0.3em](A,B,C)
	\end{scope}

	\begin{scope}[yshift=-1.5cm]
		\tkzDefPoints{0/0/A, 2/0/B, 3/0/C,  -3/0/a, -1/0/b}
		\tkzDrawSegment[xianduan={below=0pt}](a,b)
		\tkzLabelSegment[above](a,b){$a$}
		\tkzDrawLine[add=0 and 0.1](A,C)
		\tkzLabelLine[pos=1.1,right=1em](A,C){乙}
		\tkzDrawSegment[xianduan={below=0pt}](A,B)
		\tkzDrawSegment[dim={$a$,-10pt,}](A,B)
		\tkzLabelPoints[above=0.3em](A,B,C)
	\end{scope}
\end{tikzpicture}

